Over the recent years, a management system for conducting inventory management and physical distribution management of products, parts, etc has involved utilizing a RFID (Radio Frequency Identification) technology. In the system using this RFID technology, wireless communications are performed between the wireless tag and a reader/writer (which will hereinafter be simply referred to as an interrogator), and the interrogator reads identifying information etc stored in the wireless tag. The wireless tag is also called a RFID tag, an IC (Integrated Circuit) tag, etc.
In the following patent document 1, a system which manages a multiplicity of stacked discs such as CDs and DVDs is proposed as the management system using the RFID technology described above. In this management system, the IC tag is attached to the disc, and the interrogator is connected to a holder inserted into a central hole of the disc. Further, this document discloses that the holder is configured as a slot antenna by having a hollow pipe shape and forming a slot elongated in a longitudinal direction of a hollow pipe.
Further, the following Non-Patent document 1 proposes a technology related to a slot cylinder antenna.    [Patent document 1] Japanese Patent Laid-Open Publication No. 2006-39967    [Non-Patent document 1] John D. Kraus Antennas 3rd Edition McGraw-Hill Science/Engineering/Math, Nov. 12, 2001, pp 321-322